Let's say I wanted to set up a website that allowed users to trade stocks. I would provide extra value through various services, but would rather not deal with setting up a back-end brokerage system. What are my options? So far the only option I have come up with is Interactive Brokers. I could probably use their API to execute the customer orders. Are there comparable API's from other online brokers? What kind of an account would I need to set up with IB - an Introducing Broker account, or a Financial Advisor account? Are there any gotchas that I should consider? Thanks for your help!